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Longer and less overlapping food webs in anthropogenically disturbed marine ecosystems: confirmations from the past

机译:人为干扰的海洋生态系统中更长和更少重叠的食物网:过去的确认

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摘要

The human exploitation of marine resources is characterised by the preferential removal of the largest species. Although this is expected to modify the structure of food webs, we have a relatively poor understanding of the potential consequences of such alteration. Here, we take advantage of a collection of ancient consumer tissues, using stable isotope analysis and SIBER to assess changes in the structure of coastal marine food webs in the South-western Atlantic through the second half of the Holocene as a result of the sequential exploitation of marine resources by hunter-gatherers, western sealers and modern fishermen. Samples were collected from shell middens and museums. Shells of both modern and archaeological intertidal herbivorous molluscs were used to reconstruct changes in the stable isotopic baseline, while modern and archaeological bones of the South American sea lion Otaria flavescens, South American fur seal Arctocephalus australis and Magellanic penguin Spheniscus magellanicus were used to analyse changes in the structure of the community of top predators. We found that ancient food webs were shorter, more redundant and more overlapping than current ones, both in northern-central Patagonia and southern Patagonia. These surprising results may be best explained by the huge impact of western sealing on pinnipeds during the fur trade period, rather than the impact of fishing on fish populations. As a consequence, the populations of pinnipeds at the end of the sealing period were likely well below the ecosystem's carrying capacity, which resulted in a release of intraspecific competition and a shift towards larger and higher trophic level prey. This in turn led to longer and less overlapping food webs.
机译:人类对海洋资源的开采的特点是优先清除了最大的物种。尽管这有望改变食物网的结构,但我们对这种改变的潜在后果的了解相对较差。在这里,我们利用了古代的消费组织,利用稳定的同位素分析和SIBER评估了由于顺序开采而导致的全新世后半段到整个大西洋下半年西南大西洋沿海海洋食物网结构的变化。猎人,西方海豹捕猎者和现代渔民的海洋资源。样品是从贝壳坑和博物馆中收集的。潮间带草食性软体动物和考古用软体动物的壳被用来重建稳定同位素基线的变化,南美海狮Otaria flavescens,南美海狗Arctocephalus australis和麦哲伦企鹅Spheniscus magellanicus的现代和考古骨骼被用来分析变化在顶级掠食者社区的结构中。我们发现,在中北部巴塔哥尼亚和南部巴塔哥尼亚,古代的食物网比当前的食物网更短,更多且更重叠。这些令人惊讶的结果可能最好的解释是,在毛皮贸易期间,西方海豹捕捞对pin鱼的巨大影响,而不是捕鱼对鱼类种群的影响。结果,在海豹捕捞阶段结束时的pin鱼种群可能远低于生态系统的承载能力,从而导致种内竞争的释放以及向更大和更高营养级猎物的转移。反过来,这导致更长和更少重叠的食物网。

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